Insect Management Options in Organic Farming

Phil Mulder

Professor, Interim Dept. Head, Dept. Extension Coordinator and Extension Entomologist

Department of Entomology and Plant Pathology Oklahoma State University

Oklahoma Cooperative Extension Service

Limitations under the USDA’s National Organic Program (NOP)

• Ingredients must be natural substances, or synthetics included on the National List (7CFR 205.600-205.607).

• Some natural substances are also prohibited (inert ingredients may be prohibited in some cases – See EPA List 4A or 4B).

• All substances must be approved by the Organic Materials Review Institute (OMRI) and/or the state certification agency.

• Further restrictions require preventative, cultural, and physical methods (includes release of beneficial insects) must be the first choice for pest control. If ineffective, a botanical, biological or synthetic on the national list may be used, if conditions are documented in the organic farm plan.

• This requirement reflects an historic practice relying on the use of biological and cultural practices such as; crop rotation, diversification, habitat management, beneficial organism releases, sanitation, and timing before resorting to limited use of permitted pest control substances.

Procedures and Methods in Adopting an Organic Management Plan

• Understand the pests and beneficial organisms that usually occur in the crop and anticipate the pest problems likely to occur.– Pests more effectively controlled when numbers are

low and early in their life cycles.

• Pay attention to crop rotations and crop residue incorporation, to avoid buildup in pest species. – What varieties or crops to grow– When to plant, to avoid pest problems– Good recordkeeping on pest problems – builds a

foundation for next seasons pest control strategies.

Procedures and Methods (continued)

• Correctly identify the pests and beneficial organisms present and note when they occur most commonly. – Helps alert a grower to potential problems before crop

losses occur. • Use pheromones and other trapping methods when

available for key pests, to determine timing of population cycles and predict local increases in activity.– Some cases where mating disruption can be used to

prevent successful mating, and reduce subsequent damaging populations (e.g. fruit and nut pests).

Procedures and Methods (continued)

• Make frequent or at least weekly checks for pest activity. – Use a sweep net, hand lens, drop cloth. – Inspect the underside of leaves.

• Identify tolerable levels (action thresholds) for pest activity in specific crops. – Pests feeding directly on the consumable

product can be tolerated much less than defoliators in most cases.

Specific Methods for Managing Arthropod Pests Organically

• Cultural control

• Mechanical control

• Biological control

• Chemical control

Cultural Control• Coordinate planting and harvest dates to

avoid certain pests.– Sweet corn and corn earworm– Plant later crops upwind of early crops or plant

them in isolated fields.

• Use non-susceptible cover crops to improve fertility and provide a source of organic matter. – Incorporate a grass species into a rotation, these

tend to be resistant to many insect and disease pests of common cash crops.

Cultural Control (continued)• Plant field borders or strips within the field of

species or varieties that are different from the main crop– Flowering plants along borders of fields can provide

habitat and food for beneficial insects.

• Maintain a trap crop in a vigorous state, so pests may never want to leave– Spray the trap crop if they start to leave (e.g. pearl millet)

• Manage overwintering sites for many of the true bugs (stink bugs, squash bugs, alfalfa weevils, etc.)– Lumber, box piles, storage buildings, weedy field

borders, etc.

Mechanical Control • Soil Tillage and organic matter

decomposition – Allow a longer fallow period before planting,

exposes insects to predators (e.g.- birds) or removes food supply for cutworms, wireworms, root maggots and certain mites.

• Handpicking and vacuuming certain insect pests in small plantings is quite effective– Tomato hornworms, lygus bugs, squash bugs,

etc. • Pest barriers can help in high value crops.

– Floating row covers, plastic tunnels, reflective mulches

Biological Control

• Many beneficial organisms help regulate pest numbers in nature without the aid of chemicals.

• When naturally occurring biological control is not adequate for maintaining a pest below levels that cause losses, biological control can sometimes be increased . – Classical biological control, Augmentation,

Conservation and enhancement.

Classical Biological Control• Deliberate introduction and establishment of exotic

natural enemies into areas where they did not exist. – Usually against invasive species. – Several steps in doing this properly include:

• ID the pest’s native range, search it’s native range for candidates, ship them into quarantine facilities for study to exclude contaminants and confirm that no negative impacts exist in the new country, then finally increase their numbers before release.

• Only Government agencies or University Experiment Stations – 100’s of insect and weed examples have been

successful. • Vedalia beetle on cottony cushion scale, musk thistle weevil

on musk thistle, cactus moth on prickly pear cactus, etc.

Augmentation

• Supplementing the numbers of naturally occurring natural enemies with releases of lab-reared or field collected natural enemies.– Inoculative release – building up populations of

natural enemies earlier than normal, or establishing it where it is not present.

• Releasing predatory mites in almonds or strawberries, mosquito fish in rice fields to control mosquitoes, release of bindweed mites to control bindweed in wheat, etc.

Augmentation (Continued)

• Supplementing the numbers of naturally occurring natural enemies with releases of lab-reared or field collected natural enemies.– Inundative release – periodic releases of natural

enemies with no expectations of establishment. So…. additional releases will be required throughout the season

• Releasing Trichogramma wasps for controlling caterpillar pests, release of whitefly parasitoids (Encarsia) in the greenhouse, entomopathogenic nematodes used against several soil dwelling insects,

etc.

Tips for Releasing Beneficials

• Be sure to release a sufficient amount. • Make sure adequate water is available before the

release. • Release organisms at sundown, to allow them time

to find a safe harborage• Release in specific locations where infestations are

present. • Use cages and/or beneficial insect meal to keep

insects around if pests are not present in sufficient numbers.

• Provide additional habitat when possible (includes flowering plants and clover mixes).

Conservation and Enhancement

• Modifying or enhancing the local environment to conserve beneficial species or enhancing their activities. – Increasing plant diversity in the ecosystem (e.g.

reduce monocultures). Requires careful consideration of the complex interactions between plant and animal populations.

• Habitat manipulation with cover crops, alternate hosts, insectary plants, and soil supplements to conserve

native natural enemies.

Chemical Control

• If organic growers choose to consider chemical treatment they may need to consider several factors including: – Mammalian toxicity, effects on beneficial species,

adequate coverage and volume, residual activity. • All organic materials, many of which are botanicals, are not

exclusively safer than conventional pesticides (e.g. – Nicotine is one the most dangerous substances known, yet it is considered a botanical insecticide, others like sulfur are good at suppressing certain disease problems, but may cause skin and/or eye irritation).

• For the organic grower wishing to conserve beneficial organisms, botanicals and soap-based products should be a last resort because of their broad spectrum capabilities.

Chemical Control (continued)– Effects on beneficial organisms

• Indirect effects through starvation of beneficials, which could prompt their migration out of the field.

– Adequate Coverage• Requires high volumes of water (100-200 gallons or

more per acre) with thick canopies and with certain materials.

• May require more nozzles and high pressure to produce the desired droplet size for optimum coverage (Electrostatic or airblast sprayers).

– Proper Timing is essential regardless of equipment.

• Must hit a susceptible organism at its most vulnerable stage.

Chemical Control (continued)

• Residual capacity of most organically approved materials is limited – degrade rapidly in the environment. – Repeated applications may be necessary, so

concern over resistance, but not as great with short residual materials.

– In addition, pests are unlikely to develop resistance to materials such as oils and soaps that use physical actions such as suffocation and entrapment.

Chemical Control (continued)

• Pests controlled by organically approved materials include:– Aphids: oils, soaps, pyrethrum/rotenone combinations,

kaolin clay, Pyola™(canola oil + pyrethrins) GE-derived?, garlic sprays, diatomaceous earth, Beauveria bassiana (Mycotrol O).

– May affect beneficials that are attracted to honeydew. Allow time for lag in beneficial populations before controlling aphids (e.g. greenbugs rarely need control past March 15 in southwest Oklahoma).

Chemical Control (continued)• Pests controlled by organically approved materials

include:– Whiteflies: soaps and oils (many applications), sticky traps,

seaweed powder, Beauveria bassiana (Mycotrol O).• Thorough coverage under plant leaves necessary. • First look for parasitized whitefly pupae.

Chemical Control (continued)

• Pests controlled by organically approved materials include:– Leafminers: Pyrethrins, rotenone, azadirachtin (Neem),

Entrust® (spinosad). – Sprays will slow the buildup of native wasp parasitoids.

Chemical Control (continued)

• Pests controlled by organically approved materials include:– Leafhoppers: Pyrethrins, rotenone and kaolin clay on

nymphal stages, Beauveria bassiana (Mycotrol O).

– Kaolin clay (Surround ®) acts as a deterrent, coats the plant. Leafhoppers don’t like to feed through it or get it

on their body.

Chemical Control (continued)

• Pests controlled by organically approved materials include:– Flea beetles: Soaps, pyrethrin/rotenone

combinations, sabadilla, garlic sprays, onion&mint, Pyola™(canola oil + pyrethrins) diatomaceous earth.

Chemical Control (continued)

• Pests controlled by organically approved materials include:.– Stinkbugs: Difficult to control as adults with any

materials. First two instars can be managed with soap sprays or Beauveria bassiana (Mycotrol O). Don’t let these build up or cannot be controlled. Can use traps to monitor.

Chemical Control (continued)

• Pests controlled by organically approved materials include:– Mites: sulfur sprays or dusts, mineral, vegetable-based,

or neem seed oils, kaolin clay (Surround), garlic oil. Many concoctions including glue and buttermilk sprays.

– Oil sprays: watch out if temperature and RH add up to more than 140 to avoid phytotoxicity.

Chemical Control (continued)

• Pests controlled by organically approved materials include:– Caterpillars: Bacillus thuringiensis var. kurstaki (Btk) –

Smaller worms and use thorough coverage practices, since ingestion of the material by the insects is required. Entrust®, spinosad product – quite expensive, but very effective.

Brief Lesson on Bt formulations• Make certain you are obtaining the correct

formulation for the task. – BtK – For Lepidoptera caterpillars – immature moths

and butterflies. 2-5 prolegs including anal prolegs. Thuricide cost:16 oz. = $15.46

• Don’t confuse with Hymenoptera caterpillars – immature sawflies (wasps). More than 5 prolegs. Btk will not control these insects.

• Bt’s must be ingested (foliar feeding caterpillars), paralyzes and destroys the cells of the insect gut wall, causes septecemia. Degrades rapidly in sunlight.

Brief Lesson on Bt formulations

• Make certain you are obtaining the correct formulation for the task. – Bti – var. israelensis for Diptera – immature

flies, primarily mosquitoes. (Mosquito Dunks). • May also have some effect on other fly species.• Cost: 6 pack of dunks=$17.95;

40 lb granular=$150

Brief Lesson on Bt formulations

• Make certain you are obtaining the correct formulation for the task. – Btt – var. tenebrionis or san diego for

Coleoptera larvae – immature beetles.• Marketed for elm leaf beetles, Colorado potato

beetle and may work on others.

Brief Lesson on Bt formulations

• Make certain you are obtaining the correct formulation for the task. – Bp – Bacillus popillae (Milky spore) for

Japanese beetle larvae.• Not generally effective on annual white grubs or

other scarab beetles.

• Cost – 40 oz. ~ $80

Drawing a distinction between Farming vs. Gardening

• Many organic strategies are more applicable on a small scale (home garden) but may not be practical or affordable in large acreage situations (farming).

• Organic strategies involve a personal commitment to doing things differently for the preservation of the ecosystem for the next generation.

• Organic strategies generally require more money, time and dedication to detail than conventional methods, therefore, for the farmer, there must be an economic benefit.

• IPM practitioners are always looking for compromises that incorporate organic alternatives and more eco-friendly materials into the arsenal of tools available to the farmer. These compromises (often unacceptable as organic), represent safe, eco-friendly and more economically sound approaches to pest management.– May incorporate insect growth regulators and other highly

specific insecticides not certified as organic.

List of Resources for Organic Growers

• Handout with various website and handbook resources from general information to insect guides, and insect, weed and disease management.

• Several organics catalogs available (e.g. – Arbico organics). • Several resources for IPM practitioners, which utilize several

possible mechanisms for managing pests below economically established thresholds (e.g. Great Lakes IPM).

• Excellent tutorial with detailed information on much of this presentation is available through the North Central Regional Extension Publication 401, “Alternatives in Insect Management – Biological and Biorational Approaches” by Rick Weinzierl and Tess Henn – Available on-line at: http://www.aces.uiuc.edu/vista/abstracts/aaltinsec.html